The present invention relates generally to the field of electric motors and similar machines. More particularly, the invention relates to a novel technique for making a stator for an electric motor or similar machine.
In the field of electric motors, generators, dynamos, and similar machines, a wide variety of configurations have been proposed and are presently in use. Most such machines employ a stator which surrounds a rotor. The stator and rotor may have various designs and electrical configurations depending upon the type of application, the environment in which they are used, the available power, and other such factors. A common type of electrical motor, for example, is the induction motor used throughout industry and in many varied applications. Induction motors typically employ a stator including a core in which a plurality of windings are installed. Other types of electrical machines use somewhat similar stators, with rotor designs varying from permanent magnet rotors, wound rotors, brush and brushless rotors, and so forth.
In the field of stator design, many varied approaches have been proposed. For example, conventional stators are commonly manufactured based upon a core having a series of radially-disposed slots. The slots are designed to receive the stator coils. Each slot is typically insulated by a liner, and the coils are installed in the slots with leads exiting an end of the stator. The leads are interconnected in groups and channeled within the motor housing to an exit point for connection to a source of power.
The particular arrangement of coils within a stator defines the speed and electrical machine type. For example, coils in induction motors are wired together in groups to define poles. The synchronous speed of the motor is, then, defined by the number of poles and the frequency of the power applied to the stator. Moreover, the groupings of coils will define whether the machine is suitable for single-phase power or three-phase power. A corresponding number of slots is provided in the stator core to receive the desired number of coils for the particular motor configuration.
Even for motors having similar synchronous speeds, power ratings, and so forth, a wide variety of winding patterns are presently in use. The winding patterns may be grouped, generally, into classes including lapped designs and concentric designs. In lapped designs, one leg or side of a coil is installed in a base position in a slot, while the other leg or side of the coil is installed in a position over a different coil. The coils thus must “lap” over one another at ends of the stator core. In concentric designs, on the other hand, coils installed in a base position are placed in the base position for both legs or sides of the coil. Thus, certain coils can be fully installed prior to installation of coils which will overlie the installed coils. Thus, the coils do not lap, but are concentric to one another, at least within certain groups. Significant advantages flow from concentric coil designs. For example, the coils can be preformed and installed by specially-adapted machines. In lap designs, human operators typically install the coils within the stator core due to the complexity of installing coil legs in base and overlying positions within the stator core.
Despite the advantages of concentric winding designs, there is still significant need for improved designs. For example, existing stator designs typically provide for exiting leads of the stator windings from a single end of the stator core only. Where such leads become bulky, particularly where higher numbers of coil groups are employed or for higher power or voltage applications, the available space within the motor housing may significantly limit or even make impossible the installation of the coils. Larger motor frame sizes would thus be needed for particular power ratings due to the presence of the coil leads within the end bracket of the motor.
There is, at present, a significant need for an improved motor design based upon a concentric pattern which reduces the congestion at ends of the motor due to exiting leads. There is also a need for a technique for winding and making a motor stator which accommodates machine winding of concentric coils in such new patterns. There is a particular need for a method for making four-pole motor stator for use in applications requiring such motors, and, still more particularly, for three-phase rated four-pole motors having concentric winding patterns.